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UBC Theses and Dissertations
Mapping of modern pyroclastic deposits with ground penetrating radar: experimental, theoretical and field results Rust, Alison C.
Abstract
This thesis explores the utility of ground-penetrating radar (GPR) in mapping and characterizing young pyroclastic deposits. In particular, laboratory measurements examine the relationship between porosity and dielectric constant of volcanic rocks. Simulations and field studies demonstrate how GPR data can be used to both image, and quantify, relative porosity variations in pyroclastic deposits. The laboratory results (Chapter 2) indicate a strong and definite relationship between total porosity and dielectric constant of dry, felsic to intermediate volcanic rocks. The trend formed by these data is remarkably tight and coherent, especially considering the samples derive from five deposits and two volcanoes. Chapter 3 models the propagation of a radar wave through a welded pyroclastic flow deposit of variable porosity using the porosity-dielectric constant relationship from Chapter 2. Although porosity changes are gradational, the deposit generates reflections. Distinctive signals correspond to portions with essentially constant porosity or areas where porosity changes with depth at a moderate rate. GPR data were collected on sections of pyroclastic fall and welded and unwelded pyroclastic flow deposits in Central Oregon (Chapter 4). Airfall and pyroclastic flow deposits can be distinguished on the basis of their distinct geophysical character. For example, the same characteristic signals for regions of changing porosity with depth and regions of constant porosity, which were recognized in the modeling (Chapter 3), are seen in the GPR data. The results indicate that GPR can be used to map the intensity of welding and separate zones of uniform welding from zones of variable welding. Velocity analysis of common midpoint (CMP) surveys is shown to aid in mapping facies variations, as well as, converting travel times into depths in radargrams. GPR is also found to be useful in delimiting deposit thicknesses and geometries away from exposure.
Item Metadata
Title |
Mapping of modern pyroclastic deposits with ground penetrating radar: experimental, theoretical and field results
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
1998
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Description |
This thesis explores the utility of ground-penetrating radar (GPR) in mapping and
characterizing young pyroclastic deposits. In particular, laboratory measurements examine
the relationship between porosity and dielectric constant of volcanic rocks. Simulations and
field studies demonstrate how GPR data can be used to both image, and quantify, relative
porosity variations in pyroclastic deposits. The laboratory results (Chapter 2) indicate a
strong and definite relationship between total porosity and dielectric constant of dry, felsic to
intermediate volcanic rocks. The trend formed by these data is remarkably tight and
coherent, especially considering the samples derive from five deposits and two volcanoes.
Chapter 3 models the propagation of a radar wave through a welded pyroclastic flow deposit
of variable porosity using the porosity-dielectric constant relationship from Chapter 2.
Although porosity changes are gradational, the deposit generates reflections. Distinctive
signals correspond to portions with essentially constant porosity or areas where porosity
changes with depth at a moderate rate.
GPR data were collected on sections of pyroclastic fall and welded and unwelded
pyroclastic flow deposits in Central Oregon (Chapter 4). Airfall and pyroclastic flow
deposits can be distinguished on the basis of their distinct geophysical character. For
example, the same characteristic signals for regions of changing porosity with depth and
regions of constant porosity, which were recognized in the modeling (Chapter 3), are seen in
the GPR data. The results indicate that GPR can be used to map the intensity of welding and
separate zones of uniform welding from zones of variable welding. Velocity analysis of
common midpoint (CMP) surveys is shown to aid in mapping facies variations, as well as, converting travel times into depths in radargrams. GPR is also found to be useful in
delimiting deposit thicknesses and geometries away from exposure.
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Extent |
15510216 bytes
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Genre | |
Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2009-05-26
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0053334
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
1998-11
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Item Media
Item Citations and Data
Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.